A seat back cushion of a conventional vehicle seat is elastically supported on a large number of seat springs mounted between side frames of a seat back frame. The seat springs are zigzag springs or formed wire springs in general.
There is also a known vehicle seat having a cushion plate disposed behind a seat back cushion and supported on a seat back frame by using seat springs (e.g., Patent Document 1).
There is another known vehicle seat having a cushion plate provided with an auxiliary plate that moves back and forth to thereby change cushion pressure (e.g., Patent Document 2).
Patent Document 1: JP 2006-021616A
Patent Document 2: JP 11 (1999)-206506A